CODEWITHSUNDEEP
androidandroid-volley
user4790312
user4790312

Reputation:

Android create simple volley Singleton class to prepare GET and POST method

with android Volley tutorials i'm creating simple single Singleton class as an Volley, but after prepare GET and POST method i get NullPointerException error and i can not find whats error:

AppControllert Volley singleton class:

public class ApplicationController extends Application {
    public static final String TAG = "VolleyPatterns";
    private RequestQueue mRequestQueue;
    private static ApplicationController sInstance;

    @Override
    public void onCreate() {
        super.onCreate();
        sInstance = this;
    }
    public static synchronized ApplicationController getInstance() {
        return sInstance;
    }
    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }
        return mRequestQueue;
    }
    public <T> void addToRequestQueue(Request<T> req, String tag) {
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
        VolleyLog.e("Adding request to queue: %s", req.getUrl());
        getRequestQueue().add(req);
    }
    public <T> void addToRequestQueue(Request<T> req) {
        req.setTag(TAG);

        getRequestQueue().add(req);
    }
    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}

and in Activity i'm try to create simple request with this class:

final String URL = "http://192.168.1.6/apitest";
JsonObjectRequest req = new JsonObjectRequest(URL, null,
        new Response.Listener<JSONObject>() {
            @Override
            public void onResponse(JSONObject response) {
                Log.e("Response:", response.toString());
            }
        }, new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
        Log.e("Error: ", error.getMessage());
    }
});
ApplicationController.getInstance().addToRequestQueue(req);

Logcat error:

Caused by: java.lang.NullPointerException
            at asrebidaree.ir.asrebidaree.ActivityRegistration.onCreate(ActivityRegistration.java:37)

Line 37 is : ApplicationController.getInstance().addToRequestQueue(req);

Upvotes: 1

Views: 4196

Answers (1)

Blackbelt
Blackbelt

Reputation: 157487

The code looks good. You have to register your Application's subclass in your AndroidManifest.xml. If you didn't, your sInstance will not be initialized, since Android will not use your Application's sublcass

Upvotes: 3

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